Apparatus and method to communicate information in a borehole

Claim 1

In apparatus used in borehole mapping or surveying and including instrumentation for the determination of borehole azimuth and/or tilt, the combination comprising (a) means for suspending said instrumentation in the borehole, (b) said instrumentation operating to generate analog signals in the borehole, (c) means responsive to reception of said signals for multiplexing said signals and converting same to digital signals, in the borehole, (d) means responsive to reception of said digital signals for converting said digital signals to digital words, (e) FSK means in the borehole connected to receive said words and produce signal versions thereof at an FSK signal level, (f) a two conductor wireline in the borehole connected to transmit DC voltage downwardly to said instrumentation and to transmit versions of said digital words upwardly in the borehole, (g) a mixer stage in the borehole connected to superimpose said FSK signal versions onto the DC wireline voltage for said transmission upwardly in the borehole, (h) means for stripping said signal versions off the wireline at an upper elevation and processing said signal versions to a form usable in determination of borehole azimuth and/or tilt at the level of said instrumentation in the borehole, (i) means supplying DC power on said wireline downwardly in the borehole to said instrumentation via a sub-surface power supply regulator, (j) said sub-paragraph (g) mixer stage and said sub-paragraph (h) means including inductors operating to pass said DC power but blocking said FSK signal versions from passing into said sub-paragraph (i) power supply means and into said sub-surface power supply regulator.